Phenotypic plasticity and acclimation to water deficits in velvet-grass: along-term greenhouse experiment. Changes in leaf morphology, photosynthesis and stress-induced metabolites

Wild velvet-grass (Hoicus lanatus) collected from a natural population alon g a drought gradient, previously demonstrated as genetically homogeneous, w as studied for phenotypic plasticity and acclimation mechanisms to water de ficits. A three months greenhouse experiment was designed with plants submi tted to nine levels of water availability, three months being the usual len gth of summer drought in field conditions, Aboveground biomass, total solub le proteins, free proline, free polyamines, leaf morphology, stomatal and h air characteristics, and net photosynthetic rates were analysed, and their significance discussed. Moderate drought did not damage the velvet-grass, a nd the plants grew better than without water limitation. Water stress-typic al responses were shown as time and severity dependent in ail the measured parameters. Lowest water availability treatments induced significative incr ease in free proline and soluble protein contents, as well as reductions in leaf size and aboveground biomass. Spermidine contents rose significativel y in the most severe water stress. Furthermore, velvet-grass acclimated pro gressively to long-term water limitation.